We use very high-S/N stacked spectra of $sim$29,000 nearby quiescent early-type galaxies (ETGs) from the Sloan Digital Sky Survey (SDSS) to investigate variations in their star formation histories (SFHs) with environment at fixed position along and p
erpendicular to the Fundamental Plane (FP). We define three classifications of local group environment based on the `identities of galaxies within their dark matter halos: central `Brightest Group Galaxies (BGGs); Satellites; and Isolateds (those `most massive in a dark matter halo with no Satellites). We find that the SFHs of quiescent ETGs are almost entirely determined by their structural parameters $sigma$ and $Delta I_e$. Any variation with local group environment at fixed structure is only slight: Satellites have the oldest stellar populations, 0.02 dex older than BGGs and 0.04 dex older than Isolateds; BGGs have the highest Fe-enrichments, 0.01 dex higher than Isolateds and 0.02 dex higher than Satellites; there are no differences in Mg-enhancement between BGGs, Isolateds, and Satellites. Our observation that, to zeroth-order, the SFHs of quiescent ETGs are fully captured by their structures places important qualitative constraints on the degree to which late-time evolutionary processes (those which occur after a galaxys initial formation and main star-forming lifetime) can alter their SFHs/structures.
Photonic and optoelectronic devices may offer the opportunity to realize efficient signal processing at speeds higher than in conventional electronic devices. Switches form the building blocks for circuits and fast photonic switches have been realize
d [1,2,3,4,5,6]. Recently, proof of principle of exciton optoelectronic devices was demonstrated [7,8]. Potential advantages of excitonic devices include high operation and interconnection speed, small dimensions, and the opportunity to combine many elements into integrated circuits. Here, we demonstrate experimental proof of principle for the operation of excitonic switching devices at temperatures around 100 K. The devices are based on an AlAs/GaAs coupled quantum well structure and include the exciton optoelectronic transistor (EXOT), the excitonic bridge modulator (EXBM), and the excitonic pinch-off modulator (EXPOM). This is a two orders of magnitude increase in the operation temperature compared to the earlier devices, where operation was demonstrated at 1.5 K [7,8].
